Polymeric films are used in a wide variety of applications. One particular use of polymeric films is in reflective polarizers which reflect light of one polarization for a given wavelength range and substantially pass light of the orthogonal polarization. Such reflective polarizers are used, for example, in conjunction with backlights in liquid crystal displays to enhance brightness of the display. For example, a reflective polarizer can be placed between a backlight and a liquid crystal display panel. This arrangement permits light of one polarization to pass through to the display panel and light of the other polarization to recycle through the backlight or to reflect off a reflective surface positioned behind the backlight, giving the light an opportunity to depolarize and pass through the reflective polarizer.
One example of a polarizer includes a stack of polymer layers of differing composition. One configuration of this stack of layers includes a first set of birefringent layers and a second set of layers with an isotropic index of refraction. The second set of layers alternates with the birefringent layers to form a series of interfaces for reflecting light. Another type of reflective polarizer includes continuous/disperse phase reflective polarizers that have a first material dispersed within a continuous second material that has an index of refraction for one polarization of light that is different than the corresponding index of the first material. Other types of reflective polarizer include wire grid polarizers and polarizers formed using birefringent cholesteric materials.